Electronic devices for power supplies and similar applications are conventionally provided in a protective, heat-dissipating package. Often, the device (e.g., a metal oxide semiconductor field-effect transistor, or "MOSFET") is attached to a lead-frame by a wire bonding technique. The device is then encapsulated or "potted," wherein an encapsulant is formed about the device to yield a unitary, board-mountable package device. One well-known configuration for board-mountable package is a so-called dual in-line package("DIP"), wherein electrical leads protrude from opposing sidewalls of the package. The leads are advantageously arranged to allow the package to be mounted to a circuit board by various conventional soldering processes. DIPs are widely used for packaging integrated circuits, most often in telecommunications or computer-related environments.
As with other types of electronic components, the trend in the design of power supplies has been toward achieving increased power and device density and lower device profile. As power suppliers become smaller, less space is available to provide the necessary electrical functions in order for the device to operate. This means surplus pins, that were normally available to handle case grounding functions, are no longer present on some circuits. The device density on boards also prohibits the addition of other case grounding devices, such as leads fastened to screws or studs.
A significant improvement in types of board mountable electronic devices was made in the encapsulated board mountable power supply of the type described in Stevens, U.S. Pat. No. 5,835,350, entitled "Encapsulated, Board-Mountable Power Supply and Method of Manufacture Therefor." Such a device represents a significant manufacturing advance and convenience from both a time and monetary perspective. While the invention described in Stevens provided a significant advance in the manufacture of electronic equipment, it continues to share the limitation of other new generation, smaller-sized, board mountable electronic circuits, which is the lack of a convenient method to ground the substrate of the device housed in the case with the supporting substrate upon which the device is mounted.
Accordingly, what is needed in the art is a device or method to provide a case grounding connection between a substrate of a circuit contained in a board mountable case and the substrate that supports the cased circuit as a part or component of a larger circuit. However, any improvements in power, density and profile cannot be at the expense of the electrical characteristics of the components and the overall power supply. Such a case grounding device or method may advantageously also preserve the convenience of an assembly process that permits a self-contained cased circuit to be plugged into a supporting substrate. Preferably, the technique should be cost-effective and suitable for mass production.